A social media account named after the Russian military's main air force base in Syria announced on Tuesday an end to a ceasefire agreement reached with the U.S. and Jordan in southwest Syria, citing breaches by insurgent groups. The decision comes at a time when Syrian President Bashar al-Assad stages a new offensive to retake one of the last rebel-held regions in the country.

The Hmeymim base, an airfield located in the west coast province of Latakia, is one of two major Russian-leased military installations in Syria, the other being a naval base about 40 miles down the coast in Tartous. Russian warplanes—likely based in Hmeymim—reportedly struck targets Monday in the southwestern province of Daraa, where Russia and Syria had agreed last year to a ceasefire with rebel groups attempting to overthrow Assad since a 2011 uprising backed by the U.S., Turkey and Gulf Arab states.

"The end of the period of reduced escalation in southern Syria can be confirmed after it was breached by extremist groups and illegitimate armed groups operating against Syrian government forces, while the agreement remains in the Syrian province of Idlib," the Central Channel for the Hmeymim Military Base wrote on Facebook.

The base also denied reports of civilian casualties in a later message, maintaining that "Russian bombers do not target civilian sites by any means. Our missions are limited to the destruction of the terrorist bases belonging to the Nusra Front and ISIS [Islamic State militant group] terrorists, in order to support friendly land forces advancing on the ground."

Smoke rises above opposition-held areas of Daraa during airstrikes conducted by the Syrian military, June 26, 2018. Russia-backed Syrian troops have for weeks been preparing an offensive to retake Syria's south, a strategic zone that borders both Jordan and the Israel-occupied Golan Heights.MOHAMAD ABAZEED/AFP/Getty Images

The news, which was also reported by Saudi Arabian newspaper Asharq Al-Awsat and Turkey's official Anadolu Agency, came as elite Syrian troops stormed through southern towns and villages held by various rebel groups, including elements of the Free Syrian Army and Hayat Tahrir al-Sham, a jihadi coalition recently added to the list of U.S.-recognized terrorist organizations due to its Al-Qaeda ties. Quick government gains have prompted Hayat Tahrir al-Sham to issue a series of statements calling on rebel factions to unite against the military and condemned those currently attempting to broker reconciliation deals with Damascus.

The Russian Defense Ministry, however, dismissed online reports that it had pulled out of the ceasefire the following day. In a statement, the ministry said Wednesday that the unofficial news "does not correspond to reality" and that "the Russian air base in Hmeymim in the Syrian Arab Republic doesn't have any websites or pages on social networks," according to the state-run Tass Russian News Agency. The statement came as activists reported further Russian airstrikes across towns in southwest Syria.

The apparent ceasefire collapse also occurred as airstrikes reportedly struck Damascus International Airport on Tuesday. While the attack remains unclaimed, it has been widely blamed on Israel, who rarely takes responsibility for strikes against Iranian and pro-Iran targets in neighboring Syria. The U.K.-based, pro-opposition Sputnik News highlighted reports claiming an Iranian cargo plane may have been the target.

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The official Syrian Arab News Agency said that two Israeli missiles fell near the country's main airport, without specifying the target. The channel connected the suspected Israeli attack to the Syrian military's retaking of large swathes of territory in the Al-Lajat region in Daraa, where international powers have rushed to prevent an even larger escalation between Iran and Israel.

Anticipating last year's ceasefire agreement to unravel as the Syrian military retook rebel enclaves outside the capital, the U.S. and Russia entered quiet negotiations with Jordan aimed at excluding Iranian and pro-Iran forces from taking part in the Syrian campaign. Israel considers their presence a provocation and has for years bombed military assets allegedly associated with Iran. When these forces reportedly responded to a deadly pre-emptive Israeli attack last month by launching rockets at the Israel-occupied Golan Heights, Israel retaliated with its largest aerial assault on Syria since the 1973 Yom Kippur War.

Russian President Vladimir Putin (3r-L), his Syrian counterpart Bashar al-Assad (4th-R), and Russian Defense Minister Sergei Shoigu (L) pose with Russian air force pilots during their visit to the Russian air base in Hmeymim in the northwestern Syrian province of Latakia, December 11, 2017. Russian air support has been vital in helping the Syrian military and its allies defeat insurgents and jihadis.MIKHAIL KLIMENTYEV/AFP/Getty Images

Despite their opposition to Assad, the U.S. and Jordan have stepped back their support for rebel groups as they became increasingly saturated with jihadi movements. Washington told Free Syrian Army commanders that "you should not base your decisions on the assumption or expectation of a military intervention by us" in a stern message published Saturday by Reuters. Jordan has repeatedly stated that it would not grant entry to any fighters or civilians fleeing to Syria's southern border with the kingdom, with Jordanian Foreign Minister Ayman Safadi asserting "our borders will remain closed" in a tweet Tuesday.

Iran-backed groups, such as the Lebanese Shiite Muslim Hezbollah movement, have reportedly pulled back from southwestern Syria as part of a recent agreement, but Iran has maintained that it would not leave Syria unless asked to do so by the local government. The latest airstrikes in Damascus, however, may indicate that the deal has fallen apart or did not preclude Israeli attacks elsewhere in the country. Last week, unclaimed airstrikes blamed on both the U.S. and Israel reportedly killed dozens—including Iraqi militias—in Syra's far eastern province of Deir Ezzor.

Assad has welcomed both Russia and Iran as partners in the battle against insurgents and jihadis, but he has called the U.S. and Turkey to withdraw their forces immediately. Iraq, while deeply critical of U.S. and Israeli targeting of pro-Syrian government forces, has managed to maintain close relations with both the Syria-Russia-Iran axis as well as the U.S.-led coalition against ISIS.

This article has been updated to include Russian Defense Ministry comments denying that the Hmeymim air base pulled out of last year's ceasefire agreement with the U.S. and Jordan.